SESSIONS resource definitions for EXCI connections

You indicate on the PROTOCOL attribute of the SESSIONS resource definition whether the sessions allocated on the MRO connection are for use by the external CICS® interface.

For full details of the SESSIONS resource definition, see SESSIONS resources. The following parameters are relevant to EXCI:
PROTOCOL({APPC|LU61|EXCI})
Indicates the type of protocol that is to be used for an intercommunication link (ISC or MRO).
APPC (LUTYPE6.2)
Advanced program-to-program communication (APPC) protocol. Specify this for CICS-CICS ISC.
LU61
LUTYPE6.1 protocol. Specify this for CICS-CICS ISC, for CICS-IMS, or for MRO.
EXCI
The external CICS interface. Specify this to indicate that the sessions are for use by a non-CICS client program using the external CICS interface. If you specify EXCI, you must leave SENDCOUNT blank.
RECEIVECOUNT({blank|number})
The number of MRO, LUTYPE6.1, or EXCI sessions that usually receive before sending.
For MRO, receive sessions can only receive before sending.
blank
These sessions can send only; there are no receive sessions.
number
Specifies the number of receive sessions on connections that specify blank, LU61, or EXCI on the protocol parameter of the CONNECTION definition. CICS uses the number to generate the last two or three characters of the session names (see RECEIVEPFX for details).

If you are using the default receive prefix (<), or your own 1-character prefix, specify a number in the range 1 through 999.

If you specify a 2-character prefix, the number is restricted to the range 1 through 99.

Except for external CICS interface (EXCI) connections, the RECEIVECOUNT in this system should equal SENDCOUNT in the other system.

RECEIVEPFX(<|prefix)
Specifies a 1- or 2-character prefix that CICS is to use as the first 1 or 2 characters of the receive session names (the names of the terminal control table terminal entries (TCTTEs) for the sessions).
Prefixes must not cause a conflict with an existing connection or terminal name.
< (MRO and EXCI sessions)
For MRO sessions, if you do not specify your own receive prefix, CICS enforces the default prefix—the less-than symbol (<), which is used in conjunction with the receive count to generate receive session names.

CICS creates the last three characters of the session names from the alphanumeric characters A through Z, and 1 through 9. These 3-character identifiers begin with the letters AAA, and continue in ascending sequence until the number of session entries reaches the limit set by the RECEIVECOUNT value. Note that receive session names are generated after the send sessions, and they follow in the same sequence.

For example, if the last session name generated for the send sessions is <AAJ, using the default prefix (<) CICS generates the receive session names as <AAK, <AAL, <AAM, and so on. (This method of generation of session identifiers is the same as for APPC sessions, except for the initial prefix symbol.)

Note: If you specify your own prefix, CICS generates the session names as in earlier releases, which is the same as for LUTYPE6.1 sessions.
prefix (LUTYPE6.1 sessions)
If the sessions are on LUTYPE6.1 ISC connections, you must specify a 1- or 2-character prefix. Do not use the default < symbol for LUTYPE6.1 sessions.

For LUTYPE6.1 sessions (and MRO if you specify your own 1- or 2-character prefix) CICS generates session names by appending a number to the prefix, either in the range 1 through 99, or 1 through 999. The number begins with 1 and is incremented by 1 until the specified RECEIVECOUNT is reached.

SENDCOUNT(blank|number)
The number of MRO or LUTYPE6.1 sessions that usually send before receiving.
For MRO, send sessions must send before they can receive.
blank
These sessions can receive only; there are no send sessions.

You must leave this field blank when the sessions are on an external CICS interface (EXCI) connection.

number
Specifies the number of send sessions on connections that specify blank or LU61 on the protocol parameter of the CONNECTION definition. CICS uses the number to generate the last two or three characters of the session names (see SENDPFX for details).

If you are using the default send prefix (>), or your own 1-character prefix, specify a number in the range 1 through 999.

If you specify a 2-character prefix, the number is restricted to the range 1 through 99.

Except for external CICS interface (EXCI) connections the SENDCOUNT in the sending system should equal RECEIVECOUNT in the receiving system.

SENDPFX(>|prefix)
Specifies a 1- or 2-character prefix that CICS is to use as the first 1 or 2 characters of the send session names (the names of the terminal control table terminal entries (TCTTEs) for the sessions).
Prefixes must not cause a conflict with an existing connection or terminal name.
> (MRO sessions)
For MRO sessions, if you do not specify your own send prefix, CICS enforces the default prefix—the greater-than symbol (>), which is used in conjunction with the send count to generate send session names.

CICS creates the last three characters of the session names from the alphanumeric characters A through Z, and 1 through 9. These 3-character identifiers begin with the letters AAA, and continue in ascending sequence until the number of session entries reaches the limit set by the SENDCOUNT value.

For example, using the default prefix (>) CICS generates session names as >AAA, >AAB, >AAC, and so on. (This method of generation of session identifiers is the same as for APPC sessions, except for the initial symbol.)

Note: If you specify your own prefix, CICS generates the session names as in earlier releases, which is the same as for LUTYPE6.1 sessions.
prefix (for LUTYPE6.1 sessions)
If the sessions are on LUTYPE6.1 ISC connections, you must specify a 1- or 2-character prefix. Do not use the default > symbol for LUTYPE6.1 sessions.

For LUTYPE6.1 sessions (and MRO if you specify your own 1- or 2-character prefix) CICS generates session names by appending a number to the prefix, either in the range 1 through 99, or 1 through 999. The number begins with 1 and is incremented by 1 until the specified SENDCOUNT is reached.

USERID(userid)
The preset user identifier to be used for link security checking.

If you do not specify a preset userid for link security, CICS uses the userid passed from the remote user as the userid for link security. For an external CICS interface link, this is the client userid.